MRT is based on the physical phenomenon of nuclear magnetic resonance and has been successfully used as an imaging method in medical and biophysical applications for over 15 years. It is a technique whereby the examinee is exposed to a strong, constant magnetic field, as a result of which the nuclear spins of the atoms in the examinee that were previously randomly oriented become regularly oriented. High-frequency waves can then excite these “regularized” nuclear spins to oscillate in a specific manner. This oscillating produces the actual measuring signal in the MRT, which signal is recorded by means of suitable receiving coils. The use of inhomogeneous magnetic fields, produced by gradient coils, enables the object being measured to be spatially coded in all three directions in space. The method allows free selection of the layer requiring to be imaged, as a result of which cross-sectional images of the human body can be taken in all directions. MRT as a cross-sectional imaging technique used in medical diagnostics is distinguished primarily, as a “non-invasive” examination method, by its versatile contrasting capabilities. As it enables an excellent display of soft tissue, MRT has developed into a method in many respects superior to x-ray computer tomography (CT). MRT is today based on the use of spin-echo and gradient-echo sequences permitting excellent image quality with measuring times in the order of a few seconds to minutes (depending on the specific application).
Constant technical further development of the components employed in MRT devices and the introduction of fast imaging sequences have enabled MRT to be used in an increasing number of medical applications. Real-time imaging to support minimally invasive surgery, functional imaging in neurology, and perfusion measuring in cardiology are just a very few examples.